Given a string of letters, how can I count the occurrences of every letter?

Question

Given a string of letters, I'm looking to create an object containing key value pairs with the letter as the key and the number of occurrences within the string as the value.

So given "aabccc", the function should return: { a: 2, b: 1, c: 3 }

What would be a good way to count the letters? Ideally adhering to functional programming paradigm and utilizing ES6 functionality if it's applicable. Until now I've only worked with C++ and OO so I'm working through exercises using tools and techniques outside of my comfort zone. I'm very new to all the new features of ES6 and functional programming so I'm hoping to develop the correct mindset for them.

Any insights would be greatly appreciated. Thank you.

score 1 · Accepted Answer · answered Feb 20 '19 at 05:05

1

You can use split and reduce

Here the idea is

first split string on each character.
In reduce we check for character available as key in op or not, if it is available we increase it by one. if not we make a new key with value 1.

let str = `aabccc`

let output = str.split('').reduce((op,inp)=>{
  if(op[inp]){
    op[inp]++
  } else {
    op[inp]=1
  }
  return op
},{})

console.log(output)

answered Feb 20 '19 at 05:05

Code Maniac

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Or you can you `_.reduce()` of `lodash` to skip the `split`. `_.reduce(str, (obj, c)=>{ obj[c] ? obj[c]++ : obj[c] = 1; return obj;}, {})` – bird Feb 20 '19 at 09:25

Given a string of letters, how can I count the occurrences of every letter?

1 Answers1